Fourier transform spectrometer
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Fourier transform spectrometer(FTS) A type of interferometer that is used to study the constituent frequencies of a beam of radiation and can work in many wavelength regimes. A parallel beam of radiation is split into two coherent beams, which are then recombined so that they undergo interference. The distance traveled by one beam can be changed at a uniform rate. Any difference in distance traveled produces a phase difference between the two recombining beams. Different phase differences occur for the different frequencies present in the beams. If the recombined beams are focused onto a detector and the signal displayed as a function of time, the signal increases and decreases in a complex oscillatory fashion. The signal, digitized at regular intervals, is fed into a computer, where it can be processed by means of a Fourier transform to reveal the amplitudes of all the frequencies present in the spectrum of the input radiation, i.e. the power spectrum of the source.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006